I’m sorry. Your father. I needed his pills.

Something must have happened. Gray had refused to take into account his father’s illness, his need for medication. Was his neglect a purposeful blindness, a refusal to accept his father’s true condition? Either way, his recklessness now threatened his parents’ lives.

Gray sank down, cross-legged, and stared up toward the dome. He fought to clear his mind. His worries, fears, and doubts would not serve him. Or them. Taking a deep steadying breath, he exhaled slowly and let the drone of the tourists fade into the background.

He pictured the church as it must have looked back in the sixteen-hundreds. In his mind, he repainted the walls again, whitewashing over the golden mosaics with plaster. He did so with concentrated deliberation. A meditative exercise. If only in his head, the old mosque came alive again. He heard the muezzin calling from the minarets over the ancient city. He pictured the supplicants knelt atop rugs, rising and falling, in faithful prayer.

In such a place, where would the next key be hidden? Where in all this vast space, with its countless anterooms, galleries, and side chapels?

As he sat, Gray spun his view of the church behind his eyes, like a three-dimensional computer model, studying it from all angles. As he did so, his finger absently traced in the plaster dust on the floor. He finally became aware of what he was drawing: the glyph of angelic script, the one inscribed on the back of Marco’s golden passport.

He stared down at the single letter while still spinning the architectural structure of Hagia Sophia around in his head.

“It was already a mosque,” he mumbled.

He tapped the four circles, what Vigor called diacritical marks.

Four circles, four minarets.

What if the symbol was more than the first key to solving the riddle of the coded map? What if it was meant also to be a clue leading to the second key? Didn’t Seichan say something about that? How the one key would lead to the next?

In his mind’s eye, he superimposed a schematic of Hagia Sophia over the symbol, positioning the minarets so it overlaid the diacritical marks. Four circles, four minarets. What if the symbol was supposed to also represent Hagia Sophia? A crude map with the minarets as anchors.

If so, then where to begin looking?

In the dust, Gray added an additional dotted line.

“X marks the spot,” he mumbled.

Vigor noted Gray crawling on his hands and knees near the center of the nave, sweeping the marble floor with his hands.

Balthazar noted the man’s actions with a raised eyebrow.

The two men crossed over to Gray’s side.

“What are you doing?” Balthazar said. “If you’re planning on checking the entire floor by hand, you’ll be here for weeks.”

Gray sat back, stared up at the dome as if gauging his position, then continued his sweep of the floor, working along the edge of the scaffolding. “It has to be here somewhere.”

“What?” Vigor asked.

Gray pointed back to where he had originally been seated. Vigor strode over and stared down at the smudged drawing in the dust. His brow crinkled.

Gray spoke. “It’s a rudimentary map of Hagia, indicating where we should be searching for the next clue.”

Vigor sensed the truth of Gray’s assessment, surprised yet again at the man’s unique ability to cogitate and analyze. It slightly frightened him.

Gray continued to crawl, slowly working a specific section of the floor, gaining a few strange glances from some passing tourists.

Balthazar tracked at his heels. “You think someone carved a bit of angelic script into the marble.”

Gray stopped suddenly, his shoulder brushing the black scaffolding. His fingers returned to a spot he had just swept over. He leaned down and blew on the tile.

“Not angelic script,” Gray said, and reached to his shirt collar.

Vigor joined him. Both he and Balthazar knelt around the tile that intrigued Gray. Reaching out, Vigor felt the marble with his fingertips.

Faintly inscribed in the tile, worn by ages and the erosion of treading feet, was the barest outline of a cross.

Gray pulled out the silver crucifix from around his neck. Friar Agreer’s cross. He tested its dimensions and shape against the inscription on the tile. A perfect fit.

“You found it,” Vigor said.

Balthazar already had a small rubber mallet in hand, removed from his belt. He tapped at the tile. Gray’s brow pinched at the man’s deliberate work.

Vigor explained, “It was how we found the hollow spot beneath the inscribed tile in the Tower of Winds. Percussion. Listening for any hidden cavity.”

Balthazar worked across the tile, meticulous, but the furrows across his forehead deepened. “Nothing,” he finally mumbled.

“Are you sure?” Vigor said. “It has to be here.”

“No,” Gray said. He sprawled out on his back, staring up. “What’s Jesus staring at?”

Vigor glanced to the vague figure of Christ in silver on the crucifix, then back up.

“He’s staring at the dome,” Gray answered. “The same dome that transfixed Marco Polo. A dome lightened in weight through the use of hollow bricks. If you wanted to hide something that would last the ages…”

Vigor craned, mouth wide. “Of course. But which brick?”

Balthazar leaped to his feet. “I have an idea.” He ran off toward the rear of the building, shoving through a German tour group.

Vigor offered a hand and helped Gray back to his feet. Gray collected the cross and hung it back around his neck.

“Brilliant, Gray.”

“We haven’t found the second golden paitzu yet.”

Vigor knew Gray had pulled Seichan aside for a private few words before they separated. “What’s the urgency, Gray? With Nasser coming in a few hours, why even bother finding the second key?”

“Because I want Nasser happy,” Gray said. Vigor read the worry in the young man’s eyes for his parents. “And to prove our use to him. We need him to keep us alive.”

Vigor sensed the man was leaving some bit of the plot unspoken. Before he could question Gray further, Balthazar reappeared and hurried back to them. Breathless, he held out a small tool. “With all the construction going on, I figured someone had to have a laser pointer or level. Handy when working across such vast spaces.”

Vigor’s colleague knelt down and positioned the laser device atop the inscribed cross and switched it on. Nothing seemed to happen.

Balthazar picked up a pinch of plaster dust and cast it above the device. A scintillation of ruby brilliance lit up the dust. “It’s working.” He craned up. “Someone will have to climb up the scaffolding to find which brick is lit up by the pointer.”

Gray nodded. “I’ll do it.”

Balthazar glanced around guiltily — then handed him a chisel and hammer. “I got these, too.” He waved for Gray to hide the tools away. “You’ll have to be discreet. No one’s allowed up there without a special artisan’s pass issued by the Turkish government. I got permission from the curator to allow one of us up there. To take some photographs. Briefly. But the guard”—he nodded to the armed sentinel by the scaffolding’s ladder—“in this day of terrorist attacks, they’ve been trained to shoot and ask questions later. If they see you take a chisel to the roof…” His voice trailed off.

“Beyond getting shot,” Vigor warned, “we can’t be discovered in any regard. If we’re kicked out…if the police are summoned…”

Vigor read the understanding in Gray’s eyes.

Nasser would know.

“And it’s not just our lives in jeopardy,” Vigor acknowledged.

Gray’s parents would suffer, too.

Sighing deeply, Gray lowered his voice, “Then we’ll need a distraction.”